1. Field of the Invention
The present invention relates generally to a tubular vibration-damping device for use in an automotive member mount, suspension bushing or the like, for example.
2. Description of the Related Art
Conventionally, tubular vibration-damping devices have been known as one type of vibration damping supports or vibration damping connectors interposed between components that make up a vibration transmission system in order to provide vibration damping linkage between the components. The tubular vibration-damping device has a structure in which an inner shaft member is inserted and placed into an outer tube member, and the inner shaft member and the outer tube member are elastically connected by a main rubber elastic body arranged therebetween in the radial direction. The device is employed as an automotive member mount, suspension bushing or the like.
Besides, with regard to the outer tube member, as shown in U.S. Pat. No. 7,104,533, it is possible to employ a structure which includes a flange part extending in the axis-perpendicular direction and protruding peripherally outward at one axial end thereof. During press-fitting of the outer tube member into a mounting hole of an attachment member such as a sleeve, the flange part comes into abutment against the axial end face of the attachment member so as to determine the press-fit end of the outer tube member with respect to the attachment member.
Meanwhile, whereas the outer tube member is generally formed of metal such as iron or aluminum alloy, it has been attempted to employ an outer tube member formed of synthetic resin in order to reduce its weight. FIG. 8A depicts a tubular vibration-damping device 100 of conventional construction that corresponds to U.S. Pat. No. 7,104,533. The tubular vibration-damping device 100 has a structure in which an inner shaft member 102 and an outer tube member 104 made of synthetic resin are coaxially arranged and elastically connected by a main rubber elastic body 106. The outer tube member 104 includes a flange part 108 at one axial end thereof, and is configured to be press-fitted and attached to a sleeve 110 serving as the attachment member.
However, if the outer tube member 104 formed of synthetic resin is employed, there is a risk that the outer tube member 104 may be damaged at the proximal end of the flange part 108 during press-fit mounting into the sleeve 110. Specifically, when the outer tube member 104 is mounted into the sleeve 110, the outer tube member 104 undergoes diameter-constricting deformation so that the stress due to the diameter constriction will act on the proximal end of the flange part 108. Moreover, as shown in FIG. 8B, due to the diameter constriction of the outer tube member 104, the flange part 108 inclines to the front side in the press-fit direction (axial inner side) as it goes peripherally outward, while the inclined flange part 108 is pressed against the axial end face of the sleeve 110 that extends in the axis-perpendicular direction. By so doing, as depicted in FIG. 8C, the flange part 108 deforms in the direction for which the incline angle becomes smaller so that the stress due to such deformation acts on the proximal end of the flange part 108 of the outer tube member 104. Since these stresses both act concentratedly on the proximal end of the flange part 108 of the outer tube member 104, the outer tube member 104, which is formed of synthetic resin with a smaller strength than that of metal, sometimes suffers from the damage at the proximal end of the flange part 108.